Effects Of Pulsation Frequency On Trailing Edge Plasma Actuators For Flight Control
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Effects Of Pulsation Frequency On Trailing Edge Plasma Actuators For Flight Control
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Author : Frederick William Hamlin
language : en
Publisher:
Release Date : 2012
Effects Of Pulsation Frequency On Trailing Edge Plasma Actuators For Flight Control written by Frederick William Hamlin and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
This thesis details the aerodynamic testing of a dielectric barrier discharge (DBD) plasma actuator operating over a separation step created at the trailing edge of a modified NACA 0012 aerofoil. The work focuses specifically on the use of pulsed or interrupted plasma actuation as opposed to continuously driven actuation, to increase the change in the lift produced by activating the system. The behaviour of the actuation system is characterised in a lamina flow regime at a Reynolds number of 1.33 x 105 using force balance measurements. At zero incidence the actuator produced a peak change in CL of approximately 0.015. However, this result is sensitive to changes in the interruption frequency of the plasma, by changing the plasma drive waveform the system was able to produce both positive and negative changes in lift. A relationship was identified between the change in CL produced and the ratio of the plasma interruption frequency to the natural vortex shedding frequency. This effect was investigated using both time averaged particle image velocimetry (PIV) and instantaneous phase locked PIV images captured in sequence throughout the plasma interruption cycle. The phase locked images showed how variation in the pulsation frequency was able to produce bi-directional actuation by either constructively or destructively interfering with the vortex formation from the back of the separation step. This interference in turn altered the level of separation which was occurring, altering the degree of upwash in the wake and therefore the lift generated by the aerofoil. PIV images were also gathered for device operation at a Reynolds number of 2.3 x 104; this produced a much higher ratio of DBD jet energy to that of the freestream. These conditions showed modified actuator behaviour due to the increased authority over the flow. However, the data still showed a strong interdependence on the reinforcement or destruction of the vortex street by the actuator interruption. Furthermore, work was undertaken to develop an actuator topology based on thin metallised films along with a dielectric which was hardened against the chemical and electrical stresses present in a functioning DBD device. The failure mechanisms of metallised film actuators were investigated, and actuators with lifetimes exceeding 8 hours were demonstrated. A manufacture method for a silicon polymer (PDMS) - Kapton® laminate is detailed; this is shown to be highly resistant to both electrical breakdown and chemical attack by the oxygen plasma.
High Lift Airfoil Separation Control With Dielectric Barrier Discharge Plasma Actuators
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Author : Jesse Little
language : en
Publisher:
Release Date : 2010
High Lift Airfoil Separation Control With Dielectric Barrier Discharge Plasma Actuators written by Jesse Little and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Abstract: This work examines the performance of dielectric barrier discharge (DBD) plasma actuators for controlling separation from the leading edge and trailing edge flap shoulder of a supercritical high-lift airfoil. DBD plasma actuators driven by both typical AC voltages (AC-DBD) and more developmental nanosecond duration pulses (NS-DBD) are investigated. Characterization of the two actuators shows that very different behavior is created when exciting the plasma discharge using these two waveforms. The AC-DBD plasma actuator functions through electrohydrodynamic effects that introduce zero net mass, but nonzero net momentum into the flow. Conversely, the electrohydrodynamic effects of the NS-DBD are quite weak suggesting thermal effects from rapid localized heating by the plasma are responsible for control authority. The performance of both devices as separation control actuators is tested on a high-lift airfoil system. The AC-DBD is effective for controlling turbulent boundary layer separation from a deflected trailing edge flap between Reynolds numbers of 240,000 and 750,000. Momentum coefficients for the AC-DBD plasma actuator are generally an order of magnitude lower than those usually employed for such studies yet control authority is still realized through amplification of natural vortex shedding from the flap shoulder. The corresponding lift enhancement is primarily due to upstream effects from increased circulation around the entire model rather than full separated flow reattachment to the deflected flap surface. Lift enhancement via instability amplification is found to be relatively insensitive to changes in angle of attack provided that the separation location and underlying dynamics do not change. Control authority decreases with increasing Reynolds number and flap deflection highlighting the necessity for further optimization of AC-DBD plasma actuators for use in realistic takeoff and landing transport aircraft applications. As a whole, these findings compare favorably to studies on a similar high-lift platform using piezoelectric driven zero net mass flux actuation. The NS-DBD plasma actuator is ineffective for controlling separation from the deflected trailing edge flap. However, the device is found to be superior to the tested AC-DBD plasma actuators for controlling leading edge separation and rivals the performance of a passive droop by extending the stall angle by six degrees in the Reynolds number range 750,000-1,000,000. Detailed flow diagnostics show the NS-DBD plasma actuator functions as an active trip for pre-stall incidence angles and generates coherent spanwise vortices that entrain freestream momentum into the separated region at post-stall angles. These structures are generated across all surveyed frequencies, but optimal dimensionless frequencies for controlling separation are in the range four to six depending on the incidence angle. The contrasting performance of the NS-DBD plasma actuator at the leading and trailing edge in comparison to the AC-DBD is discussed and recommendations for future work are provided.
Active Flow Control By Using Plasma Actuators
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Author : Gabriele Neretti
language : en
Publisher:
Release Date : 2016
Active Flow Control By Using Plasma Actuators written by Gabriele Neretti and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with Technology categories.
Active flow control has recently received an increasing attention since it allows to directly manipulate the flow-field around a surface only when it is effectively requested. Aerodynamic plasma actuators supplied by a dielectric barrier discharge (DBD) can be used for this purpose. Usually, sinusoidal voltages in the range 5-50 kV peak and frequencies between 1 and 100 kHz are utilized to ignite this plasma typology. The surface discharge produced by these devices is able to tangentially accelerate the flow field by means of the electrohydrodynamic (EHD) interaction. DBDs generate non-thermal plasmas characterized by low input energies and limited temperature increments. Plasma actuators can be easily designed by following the shape of the aerodynamic body and can be used over heat-sensitive surfaces. These aerodynamic devices have demonstrated to produce boundary layer modifications with induced speeds up to 10 m/s. Their use over airfoils, flaps, and blades have shown the possibility to delay the transition between laminar to turbulent regime, to prevent flow separation enhancing lift and reducing drag. Moreover, the adoption of these actuators over landing gears and trailing edges may induce a noise reduction effect. Dielectric materials, electrodes configuration, and supplying waveforms are most relevant parameters to be considered to enhance actuator performance. On a parallel plane, on/off actuation strategy is a key point in the use of these devices when utilized over aerodynamic surfaces impinged within an external flow.
Active Flow And Combustion Control 2018
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Author : Rudibert King
language : en
Publisher: Springer
Release Date : 2018-09-03
Active Flow And Combustion Control 2018 written by Rudibert King and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-09-03 with Technology & Engineering categories.
The book reports on the latest theoretical and experimental findings in the field of active flow and combustion control. It covers new developments in actuator technology and sensing, in robust and optimal open- and closed-loop control, as well as in model reduction for control, constant volume combustion and dynamic impingement cooling. The chapters reports oncutting-edge contributions presented during the fourth edition of the Active Flow and Combustion Control conference, held in September 19 to 21, 2018 at the Technische Universität Berlin, in Germany. This conference, as well as the research presented in the book, have been supported by the collaborative research center SFB 1029 on “Substantial efficiency increase in gas turbines through direct use of coupled unsteady combustion and flow dynamics”, funded by the DFG (German Research Foundation). It offers a timely guide for researchers and practitioners in the field of aeronautics, turbomachinery, control and combustion.
Airfoil Leading And Trailing Edge Separation Control Using Sdbd Plasma Actuators
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Author : Christopher L. Kelley
language : en
Publisher:
Release Date : 2013
Airfoil Leading And Trailing Edge Separation Control Using Sdbd Plasma Actuators written by Christopher L. Kelley and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
Computational Investigation Of Plasma Actuator As An Active Flow Control Strategy Of Laminar Separation Bubbles
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Author : Justin Roger Aholt
language : en
Publisher:
Release Date : 2011
Computational Investigation Of Plasma Actuator As An Active Flow Control Strategy Of Laminar Separation Bubbles written by Justin Roger Aholt and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with Actuators categories.
"A parametric computational study designed to examine the plausibility of an external body force generated by active means, such as a plasma actuator, as a means of controlling a Laminar Separation Bubble (LSB) over an airfoil at low Reynolds numbers was conducted. Computational Fluid Dynamics (CFD) was employed to characterize the effect that a body force, localized to a small region tangent to the airfoil surface, might have on an LSB. In this study, the effects of altering the strength and location of the "actuator" on the size and location of the LSB and on the aerodynamic performance of the airfoil were observed. In a separate investigation, the effects of operating an actuator in a "burst" mode are investigated, where the effects of pulsing frequency and duty cycle are examined to determine whether further performance enhancements can be achieved via such means. It was found that the body force, when properly located and with sufficient magnitude, could effectively eliminate the LSB. Additionally, it was found that by eliminating the LSB, the aerodynamic efficiency of the airfoil could be improved by as much as 60%. Thus, it was determined that such a system may indeed be an effective measure of reducing or eliminating the negative effects associated with LSBs at low Reynolds numbers. Additionally, pulsed operation of the actuator was found to enhance effectiveness by as much as 20% over a power-equivalent steady actuator. These results indicate that such a control strategy may be an excellent candidate for future experimental research regarding this topic"--Abstract, leaf iii
Recueil Pi Ces Diverses D Albert Husson Jou Es De 1952 1974
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Author :
language : en
Publisher:
Release Date : 1952
Recueil Pi Ces Diverses D Albert Husson Jou Es De 1952 1974 written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1952 with categories.
Development Of Dielectric Barrier Discharge Plasma Actuators And Their Application At Subsonic Speeds
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Author : Craig Hale
language : en
Publisher:
Release Date : 2012
Development Of Dielectric Barrier Discharge Plasma Actuators And Their Application At Subsonic Speeds written by Craig Hale and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
Plasma actuators are electrical devices that generate a wall bounded jet without the use of any moving parts. For aerodynamic applications they can be used as flow control devices to delay separation and augment lift on a wing. The aim of this project is to initially develop a system capable of generating and sustaining a plasma that generates a wall bounded jet. The next step is to investigate the effect of varying the number and distribution of encapsulated electrodes in the dielectric layer. Finally the best case design is applied at the leading edge and flap shoulder of a NACA0015 aerofoil with a 20% flap. Utilising a transformer cascade, plasma has been generated for a variety of input voltages. In the quiescent environment of a Faraday cage the velocity flow field is recorded using particle image velocimetry (PIV). Through understanding of the mechanisms involved in producing the wall jet and the importance of the encapsulated electrode a novel actuator design was investigated. The actuator design distributes the encapsulated electrode throughout the dielectric layer. The experiments have shown that actuators with shallow initial encapsulated electrodes induce velocities greater than the baseline case at the same voltage. Actuators with a deep initial electrode are able to induce the highest velocities as they can operate at higher voltages without breakdown of the dielectric. The best actuator case is applied to the aerofoil for Reynolds numbers of 1:97x105, 2:63x105 and 3:29x105. The lift and drag are recorded using pressure measurements around the aerofoil surface and across the aerofoil's wake. PIV is utilised to visualise the flow field. The trailing edge actuator produces a step increase in lift for pre-stall angles of attack and delays stall by 1° at Re = 1:97x105. The leading edge actuator has limited impact on the flow for the no flap deflection case due to the actuator location. As the flap deflection increases the leading edge actuator is able to influence the flow. Repositioning of the leading edge actuator has the ability to reattach the flow around the fore portion of the aerofoil at a post stall angle of alpha = 18°.
Prevention Of Dynamic Stall Using High Frequency Plasma Actuators
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Author : Alexander James Lilley
language : en
Publisher:
Release Date : 2023
Prevention Of Dynamic Stall Using High Frequency Plasma Actuators written by Alexander James Lilley and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023 with categories.
serpentine style actuators, and a wire plate actuator. The best-performing actuator is identified as the wire-plate configuration where the wire is embedded in the wing leading edge. This is coined as the Linear Counter-flow with Point Embedded Electrode (LCPEE) that prevents dynamic stall for the range of motion studied while providing little passive delay. The LCPEE actuator is then tested for a higher angle of attack sinusoidal motion between alpha=6 to alpha=20 at the reduced frequency of k=pi/16. For the angles observed no flow reversal occurred. In addition to dynamic stall control, the validity of plasma actuators as practical flow control devices has been demonstrated by identifying their ability to quickly recover thrust performance under wet conditions.
Liste Compl Te De Messieurs Les D Put S Aux Etats G N Raux De Leurs Adjoints Suppl Ants Avec Diff Rentes Observations Les D Liberations Du Haut Clerg De La Noblesse De Bretagne 1789
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Author :
language : en
Publisher:
Release Date : 1789
Liste Compl Te De Messieurs Les D Put S Aux Etats G N Raux De Leurs Adjoints Suppl Ants Avec Diff Rentes Observations Les D Liberations Du Haut Clerg De La Noblesse De Bretagne 1789 written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1789 with categories.